The workers were categorized into two exposure groups according to the individual exposure level: low-level exposure group (mean lifetime dose of electric field strength: 288 V²h/m² (UHF), 6570 V²h/m² (VHF), 6848 V²h/m² (UHF+VHF); mean value: 0.1 V/m (UHF), 0.3 V/m (VHF), 0.3 V/m (UHF+VHF); maximal value: 5.3 V/m (UHF), 0.9 V/m (VHF), 7.9 V/m (UHF+VHF)) and high-level exposure group (mean lifetime dose of electric field strength: 130 130 V²h/m² (UHF), 640 583 V²h/m² (VHF), 771 200 V²h/m² (UHF+VHF); mean value: 1.1 V/m (UHF), 2.5 V/m (VHF), 2.7 V/m (UHF+VHF); maximal value: 6.8 V/m (UHF), 15.2 V/m (VHF), 16.7 V/m (UHF+VHF)).
|Reference group 1||unexposed workers|
|Group 2||low-level exposed workers|
|Group 3||high-level exposed workers|
36 (51%) out of 71 of the exposed workers reported cardiovascular symptoms, including dyspnoea, pain or discomfort in the chest or feeling of irregular heartbeat. In the control group, similar complaints were reported by 15 (29%) workers. The heart rate was higher among the exposed workers than among the unexposed workers. Standard deviation of RR intervals was found to be significantly lower in the low level-exposed group (mean +/- standard deviation 42.5 +/- 24.7 ms) compared to the control group (62.9 +/- 53.5 ms). The risk of lowered standard deviation of RR intervals was significantly increased (OR 2.37; p=0.023) in high level exposed group. Both exposed groups presented significantly higher very low and low frequency power spectrum values than the control group. The exposed groups were characterized by the dominance of the sympathetic system (low frequency/high frequency ratio 1.3 +/- 0.35).
The authors concluded that exposure to radiofrequency electromagnetic fields may affect the neurovegetative regulation of the cardiovascular system.